The present invention relates to the servicing of nuclear steam generators, and more particularly, to the installation of nozzle dams for permitting servicing to proceed within the steam generator while the nuclear reactor core is being refueled or otherwise serviced.
A variety of manually installed nozzle dams have been used in nuclear power plants, such as the type shown in U.S. Pat. No. 4,482,076, "Nozzle Plug For Submersible Vessel", and U.S. Pat. No. 4,483,457 "Hinged Steam Generator Nozzle Plug". These have proven effective in isolating the drained steam generator lower head area from the water in the steam generator hot or cold leg during reactor refueling, and thus have saved considerable time in total plant outage. Nevertheless, the manual installation of these plugs requires that many "jumpers" sequentially enter and exit the steam generator due to the high radiation in the steam generator head, even when drained.
The cost, duration of time, and exposure to radiation of the "jumpers" would be reduced considerably if the nozzle could be installed remotely. This is a difficult task, however, in that the nozzle dam components are heavy, and the space available in the head for maneuvering, is limited.